Pneumatic hammer.



No. 719,027. PATBNTBD JAN. 27, 1903.

W. T. MooooK. PNEUMATIG HAMMER.

APPLICATION FILED JAN. 30, 1902. H0 MODEL.

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No. 719,027. PATENTBD JAN. 27, 1903.

W. T. MooooK.

PNBMATIG HAMMER. APPLICATION .IIL'BD JAN. so, 1902.

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iVIIiIlIAh'I T. MCCOOII, OF RICHMOND, VIRGINIA.

SE'EUIFm'aTOll forming part of Letters Patent No. 719,027, dated January 27, 1903.

Application filed January 30, 1902. Serial No. 91,825. (No model.)

Be it known that I, NVILLIAM T. MCCOOK, a citizen of the United States, and a resident ot' Richmond, in the county of IIen rico and State of Virginia, have invented certain new and useful Improvements in Pneumatic Hammers, of which the following is a speciiication.

My invention relates to that class of tools known as pneumatic or automatic hamn'iers or impact-tools7 and which are used for chipping, riveting, calking, and similar operations; but the principles which my in vention embodies may be also applied to machines used in otberarts, such as hot-air engines, pumps, steam and gas engines, dto.

In antomatichammers and similar tools and engines it is desirable that the motive duid shall be used in as economical a manner as possible, that the reciprocating parts shall be properly cushioned at the ends ot' theirstrokes, that the use of the tool may be attended with as little discomfort to the operator possible, that the tool may be always ready for use, and that the torce of the blow delivered by and the length of stroke of the hammer may be under the control of the operator. The force of the blow delivered by the hammer is regnlated to some extent in some hammers by wire-drawing the air or other motive fluid; but this method is not always a satisfactory one, particularlyin the case of portable pneumatic hammers. A more desirable method by which to regulate the force of the blow is that in which the length ot the stroke of the reciprocating piston or hammer is regulated, and such a regulation, combined with that obtainable by wire-drawing the motive l'luid, enables the operator to obtain any force of blow between the limits of absolute rest and the heaviest blow ot' which the ham meris capable. It is now the general practice to use different hammers having different lengths of stroke for dillerent classes of work. This means a large outlay in first cost in works of any extent, for l'requently live or six hammers are necessary to properly perform the varied work which could readily be accomplished by one ham mer having an adjustable stroke. Many hammers have a deadpoint 7-that to say, there is a certain position oi' the distributing-valve when the tool cannot be started by simply turning on the air-pressure. The hammer then has to be shaken or struck in order to move the valve to start the tool. Other desirable features of an automatic hammer and of similar tools are simplicity and strength. The severe nature of the work to which they are put renders any complicated or delicate parts unsuitable, and such parts are rapidly put out of order by dirt and are troublesome to clean.

The objects of my invention are to provide a simple, strong, economical, and efficient hammer, a hammer whose stroke shall be adjustable, a hammer having a simple positive hand-valve to control the admission of the motive fluid to vary the rapidity of the stroke, Whatever its length, a hammer that shall be self-starting, and a hammer having its reciprocating parts cushioned to prevent undue wear and jar. These objects I obtain by the invention hereinafter described, and which consists in the improved form and arrangement ot' the valve for regulating the admission of the motive fluid, in the improved form and arrangement of iiuid-distrilniting valve, in the improved form of hammer and pressure-chamber, in the arrangement of the passages connecting the pressure-chamber with the chamber of the distrilniting-valve, and in the novel means for regulating the length of the stroke of the hammer.

In the drawings which form a part of this specification, and in which like numerals refer to like parts in the diierent views, Figure I is a side view of the tool, partly in section. Figs. II, III, IV are sections taken on lines a b, c d, and ef, respectively, in Fig. I. Fig. V is a front view of the cap or head of the tool. Figs. VI and VII are the end View and side elevation, respectively, of the stroke-adjusting tube. Fig. VIII is a front view of the admission-valve. Fig. IX is a broken viewshowing in section the distributing-,valve chamber. Figs. X to XVI are sectional views illustrating the manner in which the tool opcrates.

In Figs. I and X to XV, inclusive, l is the body of the hammer. 2 is the cap or head, connected with which is the handle 3. This The bore 3 is connected with the ICO IVO

hammer-body by means of a passage 7, the admission of the compressed air or other operating uid to the said passage 7 being controlled by means of avalve 6, the construction of which will be explained hereinafter. The passage 7 connects with the passage 9 in the cap 2, which passage 9 is continued in the hammer-body 1, preferably to one side of the distributing-valve chamber 9, and opens into the latter through a port 10. (See Fig. IX.) 8 is an extension of the passage 9, and it enters a chamber 12 bya port 8a, Fig. IX. The chamber 12 opens at one end into and forms an extension of the distributing-valve chamber 9a and is of smaller sectional area than the latter. (In Figs. X to XVI, inclusive, the passage 8 and others to be mentioned hereinafter are, for the sake of making the operation of the ham mer clear, shown in positions'dierent from those in which they are shown in the other figures.) Given a constant pressure in the passage 9, we have a constant pressure in the chamber 12. The distributing-valve chamber is preferably fitted with a liner 10a, made of suitable hardened material, to take the Wear occasioned by the movement ofthe valve. The distributing-valve comprises the heads 11, 13, and 14, and these said heads are connected by means of the parts 15 and 15a, the said connecting parts being less in diameter than the valve-heads, so as to provide annular spaces around the valve between the said valve-heads.

16 and 17 are exhaust-ports connecting the distributing-valve chamber with the outer air. In the chamber l2 there is a plunger 18, which plunger is always exerting a rearward pressure, since the fluid-pressure in the passage 8 and the chamber 12 is constant.

19 is an exhaust-port cut into the chambers 9a and 12 to insure the absence of pressure on the adjacent ends of the main valve and the plunger. ln the drawings I have shown the distributing-valve and the plunger 18 as formed in two separate parts. Their separation is advisable for structural reasons, but they may be made in one piece, thus forming a valve having an extension of smaller diam eter.

20 is a port through which and the passage 2l the distributing-valve chamber 9a is connected With the forward end of the pressurechamber 22.

23 is a port through which and the passage 24 the distributing-valve chamber 9 is connected with the rear end of the pressure-chamber 22.

25 is the stroke-adj usting tube,which is provided at one end with suitable means, such as a slotted head 31, for turning it and at its other and open end with a check-valve. This valve may be of any simple form and preferably consists of a ball 30, held by means of a light spring 30a against a seat formed either in the end of the adjusting-tube 25 or in the chamber in which the tube is located and adjacent to the open end of the tube. The said tube is provided in its length with openings For instance, if four different lengths ofl strokes are desired the tube 25 is provided with four ports, and four corresponding ports are provided connecting the tube-chamber with the pressure-chamber. strokes are desired, then tive sets of corresponding ports are provided, and so on. The diameter of the tube 25 should be such that the desired number of ports may be cut in it and so spaced around it that not more than one of them can afford means of communication between the interior of the tube and the pressure-chamber at any one time-that is, for any one position of the adjusting-tube.

The open end of the adjusting-tube 25 is in communication through the check-valve 30 with the passage 36, which passage connects with the passage 37, leading to the distributing-valve chamber, and with the passage 38, leading to the pressure-chamber extension 39.

40 is an exhaust-port. connecting the pressure-chamber extension 39 with the outer air, and it is located in the same vertical plane as the passage 38.

41 is the hammer, provided with a head 42 and having in its body an annular groove 43. When the hammer is in its foremost position, the groove 43 forms a connection between the passage 38 and the exhaust-port 40.

44 is the head portion of a chisel or other tool inserted in a socket 45 in the end of the body 1, and 46 is an exhaust-port connecting the space between the chisel and hammer 4l with the outer air.

The operation of my improved hammer is as follows: The hammer is to be set for the longest stroke, let us say.y The adjustingtube25 is turned in its chamber until the rearmost tube-port 26 registers with its corresponding pressure-chamber port 32. Ports 33, 34, and 35 are closed, it will be seen. The rear end of the distributing-valve is open to exhaust, Fig. X, by way of the passages 37 and 38 and the exhaust-port 40. The airpressure, which is constant in the plungerchamber l2 and which enters it by way of the passages 8, 9, and 7 and the admissionvalve 6, forces the plunger against the distributing-valve and holds it in its rearward position. Air is entering the forward end of the distributing-valve chamber by the passages 7 and 9 and by that part of the port 10 which is not covered by the valve center head 14, and it is iiowing ont by the passage 21, the outlet of which into the pressure-chamber 22, however, is closed by the hammer-head 42.

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Consequently the hammer is inoperative so long as the hammer is allowed to remain in this position. This is the mostadvantageous feature of my hammer, as will be seen hereinafter. When the hammer is in this position, its forward end is in contact with the tool, and the latter is not quite home in its socket. If the tool is now pressed against the work or is pulled back by hand, the hammer will be pushed to the position shown in Fig. XI. The air entering the distributing-valve chamber now finds its way by port 2O and passage 21 to the forward side of the hammerhead and causes the hammer to make its back stroke, the air behind the hammer in the pressure-chamber 22 exhausting through the passage 24, port 23, distributing-valve chamber, and exhaust-port 16. It willbe seen that the passage 38 is now closed by the hammerbody to exhaust. The hammer continues its back stroke until the hammer has passed and uncovered the port 32, as shown in Fig. XII. Instantly air escapes by ports 32 and 26, tube 25, check-valve 30, and passages 36 and 37 to the rear of the distributing-valve, and since the distributing-valve is of greater sectional area than the plunger 1S the pressure on it overcomes the pressure in the plunger-chamber, and it (the distributing-valve) is forced forward. With the forward movements of the distributing-valve its head 13 closes the exhaust 16 and its head 14 opens the port 10. (See Fig. XIII.) Also the head 11 uncovers the exhaust-port 17, putting the said port in communication with the forward end of the pressure-chamber through the port 2O and passage 21. Consequently the air-pressure in front of the hammer-head escapes by the exhaustport 17. The air-pressure on therear end of the distributing-valve and in the passage 37 is prevented by the check-valve 30 from escaping through the tube 25, pressure-chamber, and passage 21, and it cannot escape by way of passage 38 and exhaust-port 40, for the said passage and port are closed by the body of the hammer. Pressure now enters the rear end of the distributing-valve chamber, by the port 10 and passing by way of the port 23 and passage 24 to the rear end of the pressure-chamber 22 cushions the hammer and reversing its motion causes it to make the forward stroke. The air in the passage 37 and in the rear end of the distributingvalve will hold the said valve in its forward position during the forward stroke of the hammer; but should the pressure of this air be lessened by leakage it will be reinforced as soon as the hammer-head has passed on the forward stroke the port 32, Fig. XIV, by air passing from the rear end of the pressurechamber by way of the ports 32 and 26, the tube 25, and check-valve 30. At the completion of the forward strokes the air-pressure on the rear end of the distributing-valve escapes by the passages 37 38, groove 43 in the hammer-body, and exhaust-port 40, and the constant pressure in the chamber 12 immedi- -of passage 24 and exhaust-port 16.

ately forcesthe plunger 18 and consequently the distributing-valve to their rearward positions, as shown in Fig. X. The pressurechamber 22 is now open to exhaust by way The airport 10 is now open to the forward end of the distributing-valve chamber and air-pressure again passes through port 2O and passage 2l to the forward end of the pressure-chamber. Now when the tool lis in use the hammer at the end of its forward stroke does not advance to the position shown in full lines in Fig. XV, but it only advances to about the position shown in Fig. XVI, when the forward end of the hammer strikes the head of the chisel or other tool 44, inserted in the socket 45, Fig. L; but if the hammer remained in this position the opening of passage 21 into the pressurechamber 22 would still be closed by the hammer-head 42 and air could not enter the pressure-chamber to cause the hammer to make its backward stroke. The following is what actually takes place: The hammer advances sufficiently far to put the passage 38 in communication with the eX- haust-port 40 by Way of the groove 43, when the hammer strikes the head of the tool 44 and upon striking the hammer rebounds far enough to enable its head to uncover the passage 21, as shown in Fig. XI. Air under pressure at once enters the forward end of the pressure-chamber and causes the hammer to make its back stroke.

As hereinbefore stated, the fact that the hammer can under certain conditions advance so far as to let its head cover the airinlet passage 21 is a great advantage. For instance, the tool cannot work unless the chisel is actually in use on the work, and thereby a great saving in air is effected. Suppose, for instance, that the operator forgets to close his admission-valve when he takes the tool from the work, or suppose the valve sticks, as valves used in pneumatic tools sometimes do, the hammer makes but one or a part of one stroke and stops, for the advanoinghammerwill upon striking the chiselhead simply drive the latter forward, and should the chisel afford sufficient resistance to cause the hammer to rebound the hammer would only make one or more strokes, when it would come to rest. Again, suppose that the chisel becomes so fast in the socket that the operator cannot remove it by hand. All he has to do is to admit a small quantityl of air by the admission-valve 6, when the hammer making a stroke will loosen the chisel and then come to rest. Now when not in use on work and the hammer makes its forward stroke the forward side of the hammer-head 42 would drive up hard against the forward end of the pressure-chamber 22 were it not cushioned. I obtain a cushioning at the end of an extreme forward stroke, and so prevent jar by carrying the pressure-chamber 22 a little distance beyond the opening of the passage 21. As soon as the hammer-head IOO IIP

covers the said passage-opening it imprisons between itself and the end of the pressurechamber a sufficient quantity of the air to form an effective cushion. This is clearly shown in Figs. X and XV. The hammer is cushioned on its back stroke in the following manner: The moment the hammer-head 42 passes and uncovers the port 32 the pressure on the back stroke is released and passing to the rear end of the distributing-valve chamber throws the latter, and so admits air under pressure by port 23 and passage 24 to the rear of the pressure-chamber.

The tool is self-starting-that is to say, the distributing-valve has no dead-point-and no matter what its position may be when the air-pressure is admitted through the admission-valve it will operate. Let us suppose that when the tool is about to be put in use the parts are in the position shown in Fig. XIII. The admission-valve is opened and air enters the rear of the chamber by the ports 10 and 23 and the passage 24. There is no pressure in the passage 37, and consequently on the large end of the distributing-valve, but there is pressure in the plunger-chamber l2. Consequently the pressure in the plunger-chamber throws the plunger and the distributing-valve to the rear, now putting the port 10 in communication with the port 2O and passage 2l. Pressure enters the forward end of the pressure chamber and passes out by the ports 32 and 26 and the adjustingtube to the passage 37. As soon as the pressure in the said passage 37 is sufficiently high the distributing-valve is thrown to its forward position again and the pressure in the passage 37 holds it there throughout the forward stroke of the hammer, which is now made, since air enters the rear of the pressure-chamber by way of ports 10 and 23 and passage 24.

The question of dead-point in the valve must not be confused with the dead-point of the hammer. The valve has no dead-point; but the hammer has one, as I have pointed out and as is clearly shown in Fig. X of the drawings; but the hammer dead-point is not a necessary orfunavoidable feature of the tool, though, as explained, a desirable one, for it can be eliminated at once by making the passage 21 enter at the extreme forward end of the pressure-chamber, as passage 24 enters at the eXtreme rear, instead of at a distance from the extreme end. The hammer-head could not then cover the end of the passage 21, and so prevent the ingress of the air.

To set the pneumatic tool for its shortest stroke, we simply turn the tube 25 in its seat until the foremost port 29 registers wit-h its corresponding pressure chamber port 35. The ports 32, 33, and 34 will now be closed by the body of the tube. Theoperation of the tool will be exactly as described above except that the hammer will only travel back far enough to uncover the port 35 instead of the port 32, as in the case of long stroke, for' as soon as the hammer-head on the back stroke passes the port 35 the air-pressure will escape by the ports 35 and 29, checkvalve 30, and passages 36 and 37 to the rear end of the distributing-valve. The pressure on the latter at once overcomes the pressure on the forward end of the plunger 18 and the valve is forced to its forward position, as in Fig. XIII. The exhaust-port 17 is now in communication with the forward end of the pressure-chamber by way of the port 2() and passage 21, and air-pressure enters the rear end of the pressure-chamber by way of the port 10 in the distributing-valve chamber, the port 23, and passage 24, checking and re- Versing the backward motion of the hammer.

It will be seen that we may obtain a number of different lengths of hammer-stroke in one and the same pneumatic tool, theirnumber depending only on the number of ports, which depends .in its turn upon the length of the pressure-chamber and the size of the adjusting-tubo. Now for every length of stroke we shall obtain, if working under a constant pressure, one hammer-blow of definite forcethat is to say, given a constant pressure and four lengths of stroke we shall obtain four different hammer-blows, and the differences between these blows will not Vary. Suppose we have strokes giving blows of one, two, three, and four pounds. If regulation is effected by the length of stroke alone, these blows will not vary and we cannot obtain blows equivalent to the fractional parts of one, two, three, and four pounds; but such fractional blows can be readily obtained by varying the pressure of the operating fluid. This is easily done by a proper manipulation of the admission-valve in combination with a proper adjustment of the length of the stroke.

In an ordinary pneumatic hammer having, say, only a four-inch stroke it would be difficult to so control the admission' of the motive fluid as to obtain a series of Very light blows equivalent, let us say, to small fractional parts of the full stroke. Toimaintain such a control would necessitate an exceeding delicate admission-valve, and even with such a Valve the operators touch unless highly trained would not be suflciently delicate; but with my improved tool the operator would first set the hammer to shortest stroke-say one inch-and by manipulating the admissionvalve he would then be much more easily able to maintain a series of light blows, for the blows now would instead of being equivalent to small fractional parts of a four inch stroke be equivalent to large fractional parts of a one-inch blow. Again, suppose that an operatorvsupplied with a fo ur-inch single-stroke hammer wishes to obtain on a delicate part of the Work a series of light blows equivalent to, say, one-eighth of full blow. If the pressure of his hand is accidentally increased by any cause, he may suddenly turn on full blow IIO and perhaps ruin the work. Rather than run that risk he will in the iirst place lay aside his four-inch hammer and use instead one of a suitable and smaller stroke. Now using the short-stroke tool-say one-inch-the light blow will be more easily maintained, as it is only about half of the new full blow, and should the full pressure be turned on accidentally the resulting blow would be but little greater than the said light blow.

In my improved tool I get the beneiit of a short-stroke tool by simply shortening the length of my hammer-stroke, and, as I have now described and explained, I can with this adjustable-stroke tool do the work that it now requires a set of several tools to do.

The admission-valve for admitting air is in the case of most pneumatic tools of great importance, and it is not infrequently one of the weak features. A. weak point in many is that they require too much eiiort on the part of the operator to open them and to hold them open. This is usually done by the thumb alone, and the strain on the thumb coupled with the vibration of the tool soon produces cramp in the hand. Another weak feature in some valves is that they are closed by means of a spring, and this spring after the tool has seen much rough usage soon gets out oi order and the valve refuses to close. To avoid the latter objection, my admission-valve is arranged to be closed bythe pressure of the incoming air, and to avoid the former objection I nearly balance the valve. It would be an easy matter to completely balance it; but it is not desirable, as then some other means would have to he provided to close 'the valve when released from the pressure of the thumb. Figs. I, VIII, and XI show the construction and arrangement of my admission-valve. Fig. I shows the valve closing the passage 7. Fig. XI shows the passage 7 open to the incoming air, and Fig. VIII showsafront viewofthe valve. is the thumbpiece, which is connected with the valve 6 by means of a stem 47. The stem 47 passes through an accurately-drilled hole in a collar or plug 48, which collar its closely in the bore 3 of the handle 3 preferably and is secured therein by means @fasst-screw orpin 49. The valve is prevented from turning in the bore 3 by means of a pin 50, which projects from the thumb-piece 5 into a slot 5l, cut inthe side of the said bore. The valve 6 consists of a hollow cylinder nearly closed at its upper end and provided with an opening 52 to allow the air to pass from the interior of the valve to the passage 7. A part of the closed end of the valve is cut away, as at 53, to allow air to pass from the interior to the upper end of the valve. blow suppose that air under a pressure of one hundred pounds to the square inch is admitted through the pipe 4 and suppose thatthe sectional area oi the valve is onequarter of a square inch and of the stem 47 one sixty-fourth of a square inch. The airpressure tending to force the valve upward,

and so close it, will be twentyiive pounds, and the air-pressure on the top of the valve (due to air which has passed the cut 53 in the top of the valve) and tending to open it will be twenty-three and seven-sixteenths pounds. Consequently the resultant air-presso re which closes the valve and which the thumb of the operator has to overcome in opening it is only one and nine-sixteenths pounds.

IE a tool the force of whose blow is only regulated by the length of the ham mer-stroke is desired, the admission valve might be omitted, for, as we have seen, the tool cannot operate-thatis, the hammer cannot continue to reciprocate-unless the chisel iitted in the tool is held up to its work. Merely lifting the chisel from the work causes the hammer t0 come to rest. l

iaving now described my invention, what I claim, and desire to protect by Letters Patent of the United States, is-

l. In an automatic hammer having an inlet-passage for the admission of the motive duid, a pressure-chamber, a hammer in the pressure-chamber, a Valve-chamber intermediate and in communication with the inletpassage and the pressure-chamber, a valve in the valve-chamber to control the flow of the motive fluid between the valve-chamber and the pressure-chamber, and au intermediate chamber in communication with the valvechamber and connected with the pressurechamber by a series of ports or passages which enter the pressure-chamber at points along its length, a check-valve controlling the connection between the intermediate `chamber and the valve-chamber, and adjustable means located in the intermediate chamber whereby the check-valve may be put in communication with the pressure-chamber through any one of the series of ports or passages entering the latter, substantially as and for the purpose described.

2. In an automatic hammerhaving an inlet-passage for the admission of the motive fluid, a pressure-chamber, a hammer in the pressure-chamber, a valve-chamber intermediate and in communication with the inletpassag'e and the pressure-chamber, a valve in the valve-chamber to control the flow of the motive fluid between the valve-chamber and the pressure-chamber, an intermediate chamber in communication with the valve-chamber and connected with the pressure-chamber by a series ot' ports or passages which enter the pressure -chamber at points along its length, a check-valve controlling the connection between the intermediate chamber and the valve-chamber, and means located in the intermediate chamber and adapted to be rotated to place the valve-chamber in communication with the pressure chamber through any one of the series of ports or passages entering the latter.

In an automatic hammer having an inlet-passage for the admission of the motive iiuid, a pressure-chamber, a hammer in the IOO IIO

pressure-chamber, a valve-.chamber intermediate and in communication with the inletpassage and the pressure-chamber, a valve in the valve-chamber to control the ow of the motive fluid between the valve-chamber and the pressure-chamber, an intermediate chamber in communication with the valve-chamber and connected with the pressure-chamber by a series of ports or passages which enter the pressure chamber at points along its length, a check-valve controlling the connection between the intermediate chamber and the Valve-chamber, and, located in the intermediate chamber, a hollow ported cylinder open at one end, and adjustable to register its port with any one of the series of ports or passages entering the pressure-chamber.

4E. In an automatic hammer having an inlet-passage for the admission of the motive fluid, a pressure-chamber, a hammer vin the pressure-chamber, a valve-chamber intermediate and in communication with the inletpassage and the pressure-chamber, a valve in the Valve-chamber to control the How of the motive uid between the valve-chamber and the pressure-chamber, an intermediate charnber in communication with the Valve-chamber and connected with the pressurechamber by a series of ports or passages which enter the pressure chamber at points along its length, a check-valve controlling the connection between the intermediate chamber and the Valve-chamber, and, located in the intermediate chamber, a hollow ported cylinder open at one end and having its Wall pierced bya series of ports at points along its length and adjustable to register any one of the said ports with a corresponding one of the ports or passages entering the pressure-chamber.

5. In an automatic hammer having an inlet-passage for the admission of the motive fluid, a pressure-chamber, a hammer in the pressure-chamber, a Valve-chamber intermediate and in communication with the inletpassage and the pressure-chamber, a valve in the Valve-chamber to control the ow of the motive uid between the Valve-chamber and the pressure-chamber, an intermediate chamber in communication with the valve-chamber and connected with the pressure-chamber by a series of ports or passages which enter the pressure-chamber at points along its length, a check-valve controlling the connection between the intermediate chamber and the valve-chamber, and located in the intermediate chamber, a hollow ported cylinder open at one end and having its wall pierced by a series ofports at points along its length and rotatable to register any one of the said ports with a corresponding one of the ports or passages entering the pressure-chamber.

6. In an automatic hammer, having a pressure-chamber, means for supplying pressure to the pressure-chamber to cause the hammer to reciprocate in its forward direction and in a rearward direction alternately, a valve controlling the direction of the flow of chamber and adapted to control the direction of the flow of the air-pressure to the pressure-chamber to cause the hammer to reciprocate, a plunger of smaller diameter than the valve bearing upon one end of the Valve, an air-passage arranged to admit a constant air-pressure to the end of the plunger remote from the valve, a passage connecting the other end of the valve-chamber with an exhaust-port and also with a port entering the pressure-chamber at a point intermediate its length, a check-valve controlling the said port, and the said exhaust-port being controlled by the body of the hammer.

8. In an automatic hammer, the combination of a pressure-chamber,a hammer adapted to reciprocate in the pressure chamber, a valve-chamber in connection with each end ot' the pressure-chamber, a valve in the valvechamber and adapted to control the direction of the now of the air-pressure to the pressurechamber to cause the hammer to reciprocate, a plunger of smaller diameter than the valve bearing upon one end of the valve, an airpassage arranged to admit a constant airpressure to the end of the plunger remote from the valve, a passage connecting the other end of the Valve-chamber with an eX- haust-port and also with a port entering the pressure-chamber at a point intermediate its length, a checkvalve controlling the said port, the said eXhaust-port being controlled by the body of the hammer, and vadjustable means for changing the position of the checkvalve-controlled port entering the pressurechamber at a point intermediate its length.

9. In an automatic hammer having a pressure-chamber, means for supplying pressure to the pressure-chamber to cause the hammer to reciprocate therein, a valve controlling the direction of thelow of pressure to the hammer, a passage connecting the pressure-chamber with the valve-chamber to allow the pressure in the pressure-chamber when the hammer is on its backward stroke to operate the Valve to change the direction of motion of the hammer, and a check-valve controlling the said passage.

lO. In an automatic hammer having a pressure-chamber, means for supplying pressure to the pressure-chamber to cause the hammer to reciprocate therein, a Valve controlling the direction of the ow of pressure to the ham- IOO IIO

mer, a passage connecting the pressure-cham loer with the valve-chamber to allow the pressure in the pressure-chamber when the hammer has reached a predetermined point on its backward stroke to operate the valve to change the direction of motion of the hammer, and a cheek-valve eontrollingthe said passage.

1l. In an automatic hammer, a pressurechamber, a valve-chamber in communication with each end of the pressure-chamber, a Valve in the valve-chamber controlling the direction of the flow of air-pressure to the pressure-chamber, means for operating the Valve in a rearward direction, a passage 'connecting the rear end of the valve-chamber With an exhaust-port 40 and with a chamber VILLIAM T. MCCOOK.

Witnesses:

M. W. PACE, C. W. THRocKMoRToN. 

